The phrase “sullen earth” evokes the pathetic fallacy. The external description of the earth reflects the speaker’s internal state: sullen and lowly. By beginning the line with “sullen earth,” the speaker sets the stage for the ascent to “heaven’s gate.”
In this line, “thee” saves the speaker from the sin of despair. “Thee” redeems the speaker in the way that religion and piety can not. In this way, the love object displaces God as a type of false idol.
